The general objective of the proposed work is to study the antigenic components of strains of Actinomyces viscosus, A. israelii and Bacteroides gingivalis, all known periodontopathic microorganisms isolated from human supra- and subgingival dental plaque. The antigens will be isolated from sonic extracts of these strains using various procedures including column chromatography, preparative polyacrylamide gel electrophoresis and isoelectric focusing. The purified antigens will be characterized chemically using amino acid, amino sugar and sugar analyses. The biological activity of each antigen will be assessed by in vitro lymphocyte blastogenesis using human peripheral blood lymphocytes from individuals with appropriate forms of periodontal disease as target cells. Patients' sera will also be examined for the presence of antibodies to the isolated antigens. The aim is to determine the specificity of the host immune response to these bacterial antigens to assist in the understanding of the role of this response in the pathology associated with human periodontal diseases.